use crate::consts::DAYSEC;

///  Time scale transformation:  Universal Time, UT1, to Terrestrial

///  Time, TT.

///

///  This function is part of the International Astronomical Union's

///  SOFA (Standards of Fundamental Astronomy) software collection.

///

///  Status:  canonical.

///

///  Given:

///  ```

///     ut11,ut12  double    UT1 as a 2-part Julian Date

///     dt         double    TT-UT1 in seconds

///  ```

///  Returned:

///  ```

///     tt1,tt2    double    TT as a 2-part Julian Date

///  ```

///  Returned (function value):

///  ```

///                int       status:  0 = OK

///  ```

///  Notes:

///

///  1) ut11+ut12 is Julian Date, apportioned in any convenient way

///     between the two arguments, for example where ut11 is the Julian

///     Day Number and ut12 is the fraction of a day.  The returned

///     tt1,tt2 follow suit.

///

///  2) The argument dt is classical Delta T.

///

///  Reference:

///

///     Explanatory Supplement to the Astronomical Almanac,

///     P. Kenneth Seidelmann (ed), University Science Books (1992)

///

pub fn ut1tt(ut11: f64, ut12: f64, dt: f64) -> Result<(f64, f64), i32> {

    let dtd = dt / DAYSEC;

    // Result, safeguarding precision.

    let (tt1, tt2) = if ut11.abs() > ut12.abs() {

        (ut11, ut12 + dtd)

    } else {

        (ut11 + dtd, ut12)

    };

    /* Status (always OK). */

    Ok((tt1, tt2))

}